This invention relates broadly to a mechanically driven air compressor adapted for use in fuel injection systems for internal combustion engines, and more particularly, pertains to an air compressor having an end cap assembly in which a crankshaft is rotated by an engine driven pulley.
It is well known that an air compressor is used to force fuel into the combustion chamber of a fuel injected internal combustion engine. The air compressor is typically driven by the internal combustion engine via a drive belt which rotates a drive pulley. The drive pulley is connected to an end cap assembly including a rotatable crankshaft structure having a upwardly extending main shaft supported by a set of upper and lower ball bearings, and a downwardly depending crankpin which is joined to a reciprocated piston via a connecting rod. The piston moves back and forth in a cylinder bore having inlets for admitting air and the piston compresses the air which is forced through a reed valve mechanism into an outlet. This outlet communicates with an air pressure control device, such as an air pressure regulating valve, for providing a constant desired outlet pressure, typically 80 psi. Excessive air is dumped into an exhaust system. Such disclosure is generally set forth in U.S. Pat. No. 5,332,368 issued Jul. 26, 1994.
Such air compressors are particularly useful for fuel injection systems used in conjunction with two-cycle internal combustion engines such as used in marine applications and the like generating substantial horsepower for their relatively small size. In such applications, the air compressor must be able to provide high pressure with the engine operating at various speeds including full throttle, or typically 6000 RPM.
Unfortunately, most air compressors currently available are designed to operate in the 2000-2500 RPM range and, when driven by an engine at full throttle, will allow severe leakage or blowby of air and oil from the crankcase past the ball bearings in the end cap assembly. A further problem occurs in the assembly of prior art air compressors where the internal structure of the end cap assembly permits the ball bearings to be pressed together or preloaded in a manner which can adversely affect the operation of the air compressor.
Accordingly, it is desirable to provide an air compressor which may be operated reliably at high speeds without serious leakage of air or oil from the crankcase past the ball bearings of the end cap assembly. It is also desirable to provide an air compressor in which the lifetime of the ball bearings of the end cap assembly is extended by preventing preloading of the bearings during assembly operations.